Counterbalance for lift-bridges.



PATENTED MAY 12, 1908.

L.'H. SHOEMAKER. GOU'NTERBALANGE FOR LIFT: BRIDGES.

APPLICATION FILED 133.25, 1908.

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INVENTOR.

WITNESSES A TTORNE Y.

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No. 887,131. PATENTED MAY 12, 1908.-

L. H. SHOBMAKER.

GOUNTERBALANOE FOR-LIFT BRIDGES;

APPLICATION FILED FEB. 25, 190B.

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WITNESSES: IN VEN TOR.

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IINITD STATE% AENT @FFICE.

LOUIS H. SHOEMAKER, OF SEWIOKLEY, PENNSYLVANIA.

COUNTERBALANCE FOR LIFT-BRIDGES.

Application filed February 25, 1908.

T 0 all whom it may concern:

Be it known that I, LoUis H. SHOE- MAKER, of Sewickley, in the county ofAllegheny and State of Pennsylvania, have invented a certain new anduseful Improvement in Counterbalances for Lift-Bridges, of which thefollowing is a full, clear, and exact description, reference being hadto the accompanying drawings, forming part of this specification, inwhich Figure 1 is a side elevation of a tower and the lifting span of abridge illustrating my' invention, the span being shown in its loweredposition; Fig. 2 is a like view showing the span in its elevatedposition.

Like symbols of reference indicate like parts wherever they occur.

The object of my invention is to provide a counterbalance for themovable or lifting span of a bridge, which counterbalance shall exert aproper force to counterbalance the span at each of the various positionsthe span assumes during the lifting operation; that is, the greatestforce is exerted in counterbalancing effort when the span is in itshorizontal position, which force is lessened as the span is lifted to avertical position, so that undue counterbalancing effort shall not atany time be exercised.

I will now describe my invention so that others skilled in the art mayemploy the same.

In the drawing, 2, 3, 4 represent the piers of the bridge. Supported onthe piers 2 and 3 is the tower 5 and extending between the piers 3 and.4 is the lifting span 6 of the bridge, which span is pivoted to thetower 5 at the pier 3. The outer end of the span 6 rests on and issupported by the pier 4. Pivoted to the tower 5 is the radial arm orarms 7, at the outer end of which is a sheave 8. Mounted on the tower 5,preferably at the top thereof, is a sheave 9. Secured to the span 6 is arope 10 which passes under the sheave 8' and over the sheave 9 and isse- Specification of Letters Patent.

Patented May 12, 1908.

Serial No. 417,768.

cured to a counterbalance weight 11 ar ranged to drop from the upperportion of the tower 5. The lifting span 6 may be raised and lowered byany suitable power mechanism. When the span 6 is in its loweredposition, the weight 11 exerts its greatest effort in lifting force, butas the span rises from the position shown in Fig. 1 to the positionshown in Fig. 2, the lifting effort of the weight 11 decreases insubstantial ratio with the decrease at the resistance offered by thespan as it assumes its vertical position.

The advantages of my invention will be appreciated by those skilled inthe art. The

arts are strong and simple and not liable to get out of order and anyinjurious force or ,jar caused by the counterbalance during the liftingof the span is avoided.

Having thus described my invention, wh at I claim and desire to secureby Letters Patent is:

1. In a lifting bridge, the combination of a lifting span, a pivoted armof less length than the length of the lifting span and provided with asheave, an elevated sheave, a counterweight, and a line extending fromthe lifting span to'the sheave on the pivoted arm, thence to theelevated sheave and connected with the counterweight; substantially asspecified.

2. In a lifting bridge, the combination of a lifting span, a pivotedradial arm of less length than the length of the lifting span andprovided with a a sheave, an elevated sheave, a counterweight, and aline extending from the lifting span to the sheave on the pivoted arm,thence to the elevated sheave and connected with the counterweight substantially as specified.

In testimony whereof, I have hereunto set -85 my hand.

LOUIS I-I. SHOEMAKER.

Witnesses:

M. ARTHUR KELLER, M. A. BARTH.

